1. Field of the Invention
The present invention relates to an apparatus and method for controlling a linear compressor with an inverter unit capable of enhancing stability of a system, by preventing a jump phenomenon due to an inductance of a motor coil of a linear compressor, and by precisely controlling the linear compressor through an inverter unit.
2. Background of the Invention
In general, reciprocating compressors serve to suck and compress refrigerant gas to thereafter discharge the compressed refrigerant gas while a piston is linearly reciprocated in a cylinder. Also, the reciprocating compressors are classified, according to a method for operating the piston, into compressors employing a recipro method and compressors employing a linear method.
The reciprocating compressor employing the recipro method is implemented such that a crank shaft is coupled to a rotary motor and a piston is coupled to the crank shaft thus to convert a rotation force of the rotary motor into a reciprocation force. However, the reciprocating compressor employing the linear method is implemented by linearly moving a piston connected to a mover of a linear motor, and thus by reciprocating the piston by a linear motion of the linear motor.
The present invention relates to a reciprocating compressor employing the linear method.
A reciprocating compressor employing the linear method is not provided with a crank shaft for converting a rotating motion into a linear motion, thus not to have a friction loss due to the crank shaft, which results in a higher compression efficiency as compared to that of typical compressors.
In the case that the reciprocating compressor is applied to refrigerators or air conditioners, a voltage is variably applied to a driving motor in the reciprocating compressor. Accordingly, a compression ratio of the reciprocating compressor can also be varied, which enables a control of a freezing capacity of the refrigerators or air conditioners.
The conventional apparatus for controlling a linear compressor includes a current detecting unit for detecting a current applied to a driving motor, a voltage detecting unit for detecting a voltage applied to the driving motor, a stroke calculating unit for calculating a stroke estimation value of the compressor based upon the detected current and voltage of the driving motor, a control unit for generating a frequency input control signal, and an inverter unit for varying a voltage applied to the driving motor by changing a driving frequency based on the frequency input control signal generated by the control unit.
The voltage detecting unit detects a voltage applied to the driving motor, and the current detecting unit detects a current applied to the driving motor. And, the stroke calculating unit calculates a stroke estimation value based on the voltage and current applied to the driving motor. The control unit changes a frequency of the driving motor based on a load within a preset range, thereby adjust the frequency with a mechanic resonation of a mechanic part. Then, the control unit applies a voltage and a current to the driving motor.
The conventional apparatus for controlling a linear compressor with an inverter unit has the following problems.
Firstly, a stroke, a gas spring, etc. are calculated based on a voltage and a current detected by the voltage detecting unit and the current detecting unit. In this case, may occur a jump phenomenon that two or more strokes are generated at the same voltage due to an inductance of a coil of the driving motor.
Secondly, the jump phenomenon causes the linear compressor to have a lowered capacity varying characteristic and controlling characteristic of the linear compressor, and the apparatus to have a degraded stability.